Arterial Stiffness: Measures of central arterial stiffness are independent predictors of cardiovascular outcomes in large prospective studies and is inversely correlated with measures of endothelial function.Arterial tonometry is a simple, reproducible method to measure, non-invasively, arterial stiffness. We have already established measures of central aortic stiffness - augmentation index and aortic pulse wave velocity - using the Sphygmocor system for applanation tonometry (AtCor Medical, Australia). Mathematical transformation of the radial pulse waveform is used to derive the augmentation index.The difference in time for the pulse waveform to reach the carotid compared to the femoral artery measures pulse wave velocity down the aorta, with faster transit associated with a 'stiffer' aorta.